﻿<p>The parameterized profile definition
defines a 2D position coordinate system to which the parameters of the
different profiles relate to. All profiles are defined centric to the
origin of the position coordinate system, or more specific, the origin
[0.,0.] shall be in the center of the bounding box of the profile.</p>

<p>The <em>Position</em> attribute of <em>IfcParameterizedProfileDef</em>
is used to position the profile within the XY plane of the underlying
coordinate system of the swept surface geometry, the swept area
solid or the sectioned spine. It can be used to position the profile at
any point which becomes the origin [0.,0.,0.] of the extruded
or rotated surface or solid.</p>

<p>The <em>Position</em> attribute should not be used if the transformation
can be specified in a containing object instead.  In particular, this
applies if the <em>IfcParameterizedProfileDef</em> is referenced as
<em>SweptArea</em> in subtypes of <em>IfcSweptAreaSolid</em> or as
<em>CrossSections</em> in <em>IfcSectionedSpine</em>.</p>

<p>Several subtypes of <em>IfcParameterizedProfileDef</em> provide
shape parameters which are optional. Sending systems should always
provide values for these parameters if possible. If these parameters
are left unspecified, receiving systems may retrieve values for them
by external reference (if a reference to an external document or library
is given; see guidance at <em>IfcProfileDef</em>), or estimate them, or
simply assume zero values.</p>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC2x2.
</blockquote>

<blockquote class="change-ifc2x">
IFC2x CHANGE&nbsp; The <em>IfcParameterizedProfileDef</em>
is introduced as an intermediate new abstract entity that unifies the
definition and usage of the position coordinate system for all
parameterized profiles. The Position attribute has been removed at all
subtypes (like <em>IfcRectangleProfileDef</em>, <em>IfcCircleProfileDef</em>,
etc.).
</blockquote>

<blockquote class="change-ifc2x3">
IFC2x3 CHANGE&nbsp; All profile origins are now in the center
of the bounding box.
</blockquote>

<blockquote class="change-ifc2x4">
IFC4 CHANGE&nbsp; <em>Position</em> attribute made optional (default: identity transformation).<br>
Several radius parameters in subtypes have been changed from optional <em>IfcPositiveLengthMeasure</em> (assumed default: 0.) to optional <em>IfcNonNegativeLengthMeasure</em> (default: unspecified).  This change allows to explicitly specify zero radius.  Sending systems shall export 0. values if parameters are known to be 0.<br>
Subtypes <em>IfcCraneRailAShapeProfileDef</em> and <em>IfcCraneRailFShapeProfileDef</em> deleted.  Rail profiles shall be modeled as <em>IfcArbitraryClosedProfileDef</em> or as <em>IfcAsymmetricIShapeProfileDef</em> together with appropriate external reference.
</blockquote>